Do I need four wires to a detached garage?

A feeder to an outbuilding is normally four conductors: two hots, a neutral, and an equipment ground, unless an older exception still applies locally. The cost line prices two hots plus a ground allowance and you should add the neutral if the subpanel needs it.

Why PVC instead of EMT?

PVC is the usual trench conduit. EMT is a thin-wall raceway for dry interior runs. The drop math does not change with the conduit type.

Is 60 amps enough for a garage?

That is a load calculation, not a voltage-drop result. Add the EV charger, compressor, and lights before you lock the feeder size.

60 Amp Detached Garage Subpanel Wire Size

An 80 ft feeder to a detached garage subpanel at 60 A.

Formula SSC-2026.1

K method · SSC-2026.1

Minimum size

4 AWG · 21.2 mm²

Single conductor set

Voltage drop

4.88 V

2.03% · end 235.1 V

Power loss

293 W

I²R at the operating current

Required ampacity

60.0 A

Each conductor 65 A

Material estimate

$398.40

3 conductors + PVC

Conductor weight

12.3 lb

5.6 kg · approximate insulated weight

Single-line and conductor gaugeLive scaled blueprint

Circle diameters track circular mils. The drawing is a schematic, not a conduit-fill layout.

Bill of materials and shopping list
Item	Net	Waste	Order	Unit price	Line total
aluminum 4 AWG · 21.2 mm²	80 ft one way	cuts excluded	3 conductors	USD	$322.40
PVC conduit	80 ft	—	80 ft	USD	$76.00

Copper versus aluminum at this run
Material	Minimum size	mm²	Drop	End voltage	Loss
aluminum	4 AWG · 21.2 mm²	21.2	2.03%	235.1 V	293 W
copper	6 AWG · 13.3 mm²	13.3	1.97%	235.3 V	283 W

Same load at other one-way distances
Distance	Minimum size	Drop	Percent	End voltage
80 ft	4 AWG · 21.2 mm²	4.88 V	2.03%	235.1 V

Show the deterministic formula

Single phase: Vdrop = 2 × K × I × D / cmil. Three phase: Vdrop = 1.732 × K × I × D / cmil. K is 12.9 for copper and 21.2 for aluminum. D is one-way feet.

Percent drop = Vdrop ÷ source voltage × 100. Green is 3% or less, amber is 3 to 5%, and red is over 5%. Power loss is I²R on the current-carrying conductors.

The smallest conductor that meets both the ampacity (125% when continuous) and the drop limit is selected. Ampacity does not include bundling or temperature correction.

Contractor sign-off

Project: 60 Amp Detached Garage Subpanel Wire Size

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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.

Engineering notes

A detached garage feeder is 240 V, 60 A, 80 ft, with a 3 percent limit. The default conductor is aluminum in PVC because the trench is long enough for the cost difference to matter. The copper row is one click away in the comparison table. This does not calculate the separate equipment grounding conductor from Table 250.122, and it does not decide whether a grounding electrode is required at the garage.

Code reference

NEC 210.19(A) and 215.2(A) informational notes recommend 3 percent on a branch circuit and 5 percent total with the feeder. Ampacity follows the 75°C column of Table 310.16 plus the small-conductor limits. Confirm the adopted edition.

Field questions

Do I need four wires to a detached garage?: A feeder to an outbuilding is normally four conductors: two hots, a neutral, and an equipment ground, unless an older exception still applies locally. The cost line prices two hots plus a ground allowance and you should add the neutral if the subpanel needs it.
Why PVC instead of EMT?: PVC is the usual trench conduit. EMT is a thin-wall raceway for dry interior runs. The drop math does not change with the conduit type.
Is 60 amps enough for a garage?: That is a load calculation, not a voltage-drop result. Add the EV charger, compressor, and lights before you lock the feeder size.